EVALUATING THE EFFECTIVENESS OF CONSERVATION WATER-PRICING PROGRAMS: REPLY

Resource /Energy Economics and Policy,

EVALUATING THE EFFECTIVENESS OF CONSERVATION WATER-PRICING PROGRAMS

Charging farmers increasing block prices for irrigation deliveries is advocated as a means of encouraging agricultural water conservation in the West. We formulated a model of a hypothetical irrigated river basin to investigate the hyrdro-economic circumstances in which such pricing leads to water conservation. Our results indicate that increasing delivery prices may encourage irrigators to make adjustments with countervailing impacts on consumptive water use and conservation. Whether these countervailing impacts combine to conserve water or increase its consumptive use must be resolved empirically. An alternative resolution of this ambiguity is to assess water prices in terms of consumptive use.Resource /Energy Economics and Policy,

Heterobimetallic ruthenium–zinc complexes with bulky N-heterocyclic carbenes: syntheses, structures and reactivity

The ruthenium–zinc heterobimetallic complexes, [Ru(IPr)2(CO)ZnMe][BArF4] (7), [Ru(IBiox6)2(CO)(THF) ZnMe][BArF4] (12) and [Ru(IMes)’(PPh3)(CO)ZnMe] (15), have been prepared by reaction of ZnMe2 with the ruthenium N-heterocyclic carbene complexes [Ru(IPr)2(CO)H][BArF4] (1), [Ru(IBiox6)2(CO)(THF)H][BArF4] (11) and [Ru(IMes)(PPh3)(CO)HCl] respectively. 7 shows clean reactivity towards H2, yielding [Ru(IPr)2(CO) (¿2-H2)(H)2ZnMe][BArF4] (8), which undergoes loss of the coordinated dihydrogen ligand upon application of vacuum to form [Ru(IPr)2(CO)(H)2ZnMe][BArF4] (9). In contrast, addition of H2 to 12 gave only a mixture of products. The tetramethyl IBiox complex [Ru(IBioxMe4)2(CO)(THF)H][BArF4] (14) failed to give any isol- able Ru–Zn containing species upon reaction with ZnMe2. The cyclometallated NHC complex [Ru(IMes)’ (PPh3)(CO)ZnMe] (15) added H2 across the Ru–Zn bond both in solution and in the solid-state to afford [Ru(IMes)’(PPh3)(CO)(H)2ZnMe] (17), with retention of the cyclometallati

N-Heterocyclic Carbene Non-Innocence in the Catalytic Hydrophosphination of Alkynes

Studies on alkyne hydrophosphination employing nickel-NHC catalysts (NHC=N-heterocyclic carbene) revealed that the free N-alkyl substituted NHCs themselves were catalytically active. DFT calculations showed the mechanism involves the NHC acting as a Bronsted base to form an imidazolium phosphide species which then undergoes rate-limiting nucleophilic attack at the terminal alkyne carbon. This mechanism explains the preference seen experimentally for reactions with aryl substituted phosphines and alkynes, while the rearrangements of the alkenyl anion formed upon P-C bond formation account for the observation of both Z- and E-regioisomers of the products

Stoichiometric and catalytic C-F bond activation by the<i> trans</i>-dihydride complex [Ru(IEt₂Me₂)₂(PPh₃)₂H₂] (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)

The room temperature reaction of C6F6 or C6F5H with [Ru(IEt2Me2)2(PPh3)2H2] (1; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) generated a mixture of the trans-hydride fluoride complex [Ru(IEt2Me2)2(PPh3)2HF] (2) and the bis-carbene pentafluorophenyl species [Ru(IEt2Me2)2(PPh3)(C6F5)H] (3). The formation of 3 resulted from C–H activation of C6F5H (formed from C6F6via stoichiometric hydrodefluorination), a process which could be reversed by working under 4 atm H2. Upon heating 1 with C6F5H, the bis-phosphine derivative [Ru(IEt2Me2)(PPh3)2(C6F5)H] (4) was isolated. A more efficient route to 2 involved treatment of 1 with 0.33 eq. of TREAT-HF (Et3N·3HF); excess reagent gave instead the [H2F3]− salt (5) of the known cation [Ru(IEt2Me2)2(PPh3)2H]+. Under catalytic conditions, 1 proved to be an active precursor for hydrodefluorination, converting C6F6 to a mixture of tri, di and monofluorobenzenes (TON = 37) at 363 K with 10 mol% 1 and Et3SiH as the reductant

Solar Energetic Particles Produced by a Slow Coronal Mass Ejection at ∼0.25 au

We present an analysis of Parker Solar Probe (PSP) IS⊙IS observations of ~30–300 keV n⁻¹ ions on 2018 November 11 when PSP was about 0.25 au from the Sun. Five hours before the onset of a solar energetic particle (SEP) event, a coronal mass ejection (CME) was observed by STEREO-A/COR2, which crossed PSP about a day later. No shock was observed locally at PSP, but the CME may have driven a weak shock earlier. The SEP event was dispersive, with higher energy ions arriving before the lower energy ones. Timing suggests the particles originated at the CME when it was at ~7.4R_⊙. SEP intensities increased gradually from their onset over a few hours, reaching a peak, and then decreased gradually before the CME arrived at PSP. The event was weak, having a very soft energy spectrum (−4 to −5 spectral index). The earliest arriving particles were anisotropic, moving outward from the Sun, but later, the distribution was observed to be more isotropic. We present numerical solutions of the Parker transport equation for the transport of 30–300 keV n⁻¹ ions assuming a source comoving with the CME. Our model agrees well with the observations. The SEP event is consistent with ion acceleration at a weak shock driven briefly by the CME close to the Sun, which later dissipated before arriving at PSP, followed by the transport of ions in the interplanetary magnetic field

Electrons in the Young Solar Wind: First Results from the Parker Solar Probe

The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations utilizing a combination of fitting to model distributions and numerical integration for $\sim 100,000$ electron distributions measured near the Sun on the first two PSP orbits, which reached heliocentric distances as small as $\sim 0.17$ AU. As expected, the electron core density and temperature increase with decreasing heliocentric distance, while the ratio of electron thermal pressure to magnetic pressure ($\beta_e$) decreases. These quantities have radial scaling consistent with previous observations farther from the Sun, with superposed variations associated with different solar wind streams. The density in the strahl also increases; however, the density of the halo plateaus and even decreases at perihelion, leading to a large strahl/halo ratio near the Sun. As at greater heliocentric distances, the core has a sunward drift relative to the proton frame, which balances the current carried by the strahl, satisfying the zero-current condition necessary to maintain quasi-neutrality. Many characteristics of the electron distributions near perihelion have trends with solar wind flow speed, $\beta_e$, and/or collisional age. Near the Sun, some trends not clearly seen at 1 AU become apparent, including anti-correlations between wind speed and both electron temperature and heat flux. These trends help us understand the mechanisms that shape the solar wind electron distributions at an early stage of their evolution

Plasma Double Layers at the Boundary Between Venus and the Solar Wind

The solar wind is slowed, deflected, and heated as it encounters Venus’s induced magnetosphere. The importance of kinetic plasma processes to these interactions has not been examined in detail, due to a lack of constraining observations. In this study, kinetic‐scale electric field structures are identified in the Venusian magnetosheath, including plasma double layers. The double layers may be driven by currents or mixing of inhomogeneous plasmas near the edge of the magnetosheath. Estimated double‐layer spatial scales are consistent with those reported at Earth. Estimated potential drops are similar to electron temperature gradients across the bow shock. Many double layers are found in few high cadence data captures, suggesting that their amplitudes are high relative to other magnetosheath plasma waves. These are the first direct observations of plasma double layers beyond near‐Earth space, supporting the idea that kinetic plasma processes are active in many space plasma environments.Plain Language SummaryVenus has no internally generated magnetic field, yet electric currents running through its ionized upper atmosphere create magnetic fields that push back against the flow of the solar wind. These induced fields cause the solar wind to slow and heat as the flow is deflected around Venus. This work reports observations of very small plasma structures that accelerate particles, identifiable by their characteristic electric field signatures, at the boundary where the solar wind starts to be deflected. These small plasma structures observed at Venus have been studied in near‐Earth space for decades but have never before been found near another planet. These structures are known to be important to the physics of strong electrical currents in space plasmas and the blending of dissimilar plasmas. Their identification at Venus is a strong demonstration that these small plasma structures are a universal plasma phenomena, at work in many plasma environments.Key PointsPlasma double layers are detected near the Venusian bow shockMultiple double layers are identified in a small amount of burst dataKinetic processes may help mediate interaction between the solar wind and induced magnetospheresPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163462/2/grl61354.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163462/1/grl61354_am.pd